TOKYO (AP) — A Japanese digital currency exchange has been hacked, and 6.7 billion yen ($60 million) worth of cryptocurrencies are gone.

Tech Bureau Corp. said Thursday a server for its Zaif exchange was hacked for two hours last week, and some digital currencies got unlawfully relayed from what's called a "hot wallet," or where virtual coins are stored at such exchanges.

Japan has been bullish on virtual money and has set up a system requiring exchanges to be licensed to help protect consumers. The system is also meant to make Japan a global leader in the technology.

Bitcoin has been a legal form of payment in Japan since April 2017, and a handful of major retailers here already accept bitcoin payments.

But the recurrence of cryptocurrency heists shows problems persist.